Prognostic significance of ischemic episodes in patients with previous myocardial infarction

Assistance for Folding of Disease-Causing Plasma Membrane Proteins

An extensive catalog of plasma membrane (PM) protein mutations related to phenotypic diseases is associated with incorrect protein folding and/or localization. These impairments, in addition to dysfunction, frequently promote protein aggregation, which can be detrimental to cells. Here, we review PM protein processing, from protein synthesis in the endoplasmic reticulum to delivery to the PM, stressing the main repercussions of processing failures and their physiological consequences in pathologies, and we summarize the recent proposed therapeutic strategies to rescue misassembled proteins through different types of chaperones and/or small molecule drugs that safeguard protein quality control and regulate proteostasis.

Comparison of long-term clinical outcomes between revascularization versus medical treatment in patients with silent myocardial ischemia

BACKGROUND

There have been limited and conflicting results regarding the prognostic impact of revascularization treatment on the long-term clinical outcomes of silent ischemia. The current study aimed to determine whether revascularization treatment compared with medical treatment (MT) alone reduces long-term risk of cardiac death of asymptomatic patients with objective evidence of inducible myocardial ischemia.

METHODS

A total of 1473 consecutive asymptomatic patients with evidence of inducible myocardial ischemia were selected from a prospective institutional registry. All patients showed at least 1 epicardial coronary stenosis with ≥50% diameter stenosis in coronary angiography. Patients were classified according to their treatment strategies. The primary outcome was cardiac death up to 10 years.

RESULTS

Among the total population, 709 patients (48.1%) received revascularization treatment including percutaneous coronary intervention (PCI, n = 558) or coronary artery bypass graft surgery (CABG, n = 151), with the remaining patients (764 patients, 51.9%) receiving MT alone. During the follow-up period, the revascularization treatment group showed a significantly lower risk of cardiac death compared with the MT alone group (25.4% vs. 33.7%, HR 0.624, 95%CI 0.498-0.781, p < 0.001). Among revascularized patients, patients with negative non-invasive stress test results after revascularization showed significantly lower risk of cardiac death compared to those with residual myocardial ischemia (8.9% vs. 18.7%, HR 0.406, 95% CI 0.175-0.942, p = 0.036).

CONCLUSIONS

In patients with silent myocardial ischemia, revascularization treatment was associated with significantly lower long-term risk of cardiac death compared with the MT alone group. The current results support contemporary practice of ischemia-directed revascularization, even in patients with silent myocardial ischemia.

From heart to brain: the genesis and processing of cardiac pain

Angina pectoris is important because of its association with heart disease and risk of death. Historically after Heberden's account of angina in 1772, the association of pain with coronary artery disease quickly followed. Within a few years, Burns suggested an etiological role for ischemia. Subsequently, theories of differential myocardial stretch dominated thinking until Lewis' chemical hypothesis in 1932, in which the local release of chemical substances during ischemia was seen as the cause of pain. This review considers how ischemia at the tissue level triggers activation of afferent nociceptive pain fibres. The afferent projections of sympathetic and vagal afferent fibres are described, with a number of methodologies cited (eg, injection of pseudorabies virus into the heart with mapping of the retrograde viral transport pathways; and elevation of neuronal c-fos synthesis in brain regions activated by capsaicin application to the heart). Our own functional neuroimaging studies of angina are also reviewed. There are 2 intriguing features of angina. The first is the poor correlation between symptoms and extent of coronary disease. The spectrum ranges from entirely silent myocardial ischemia to that of a functional pain syndrome--the 'sensitive heart'--of cardiac syndrome X. An even more difficult aspect is the wide variability in symptoms experienced by an individual patient. A new paradigm is presented which, besides considering myocardial oxygen supply/demand imbalance, also draws insights from the broader field of pain research. Neuromodulation applies at multiple levels of the neuraxis--peripheral nerves, spinal cord, and brain--and it invites exploitation, whether pharmacological or electrical, for the benefit of the cardiac patient in pain.

Effectiveness of percutaneous coronary intervention in patients with silent myocardial ischemia (post hoc analysis of the COURAGE trial)

Previous studies have suggested that percutaneous coronary intervention (PCI) decreases long-term mortality in patients with silent myocardial ischemia (SMI), but whether PCI specifically decreases mortality when added to intensive medical therapy is unknown. We performed a post hoc analysis of clinical outcomes in patients in the COURAGE trial based on the presence or absence of anginal symptoms at baseline. Asymptomatic patients were classified as having SMI by electrocardiographic ischemia at rest or reversible stress perfusion imaging (exercise-induced or pharmacologic). Study end points included the composite primary end point (death or myocardial infarction [MI]); individual end points of death, MI, and hospitalization for acute coronary syndrome; and need for revascularization. Of 2,280 patients 12% (n = 283) had SMI and 88% were symptomatic (n = 1,997). There were no between-group differences in age, gender, cardiac risk factors, previous MI or revascularization, extent of angiographic disease, or ischemia by electrocardiogram or imaging. Compared to symptomatic patients, those with SMI had fewer subsequent revascularizations (16% vs 27%, p <0.001) regardless of treatment assignment and fewer hospitalizations for acute coronary syndrome (7% vs 12%, p <0.04). No significant differences in outcomes were observed between the 2 treatment groups, although there was a trend toward fewer deaths in the PCI group (n = 7, 5%) compared to the optimal medical therapy (OMT) group (n = 16, 11%, p = 0.12). In conclusion, addition of PCI to OMT did not decrease nonfatal cardiac events in patients with SMI but showed a trend toward fewer deaths. Although underpowered, given similar outcomes in other small studies, these findings suggest the need for an adequately powered trial of revascularization versus OMT in SMI patients.

ST depression, arrhythmia, vagal dominance, and reduced cardiac micro-RNA in particulate-exposed rats

Recently, investigators demonstrated associations between fine particulate matter (PM)-associated metals and adverse health effects. Residual oil fly ash (ROFA), a waste product of fossil fuel combustion from boilers, is rich in the transition metals Fe, Ni, and V, and when released as a fugitive particle, is an important contributor to ambient fine particulate air pollution. We hypothesized that a single-inhalation exposure to transition metal-rich PM will cause concentration-dependent cardiovascular toxicity in spontaneously hypertensive (SH) rats. Rats implanted with telemeters to monitor heart rate and electrocardiogram were exposed once by nose-only inhalation for 4 hours to 3.5 mg/m(3), 1.0 mg/m(3), or 0.45 mg/m(3) of a synthetic PM (dried salt solution), similar in composition to a well-studied ROFA sample consisting of Fe, Ni, and V. Exposure to the highest concentration of PM decreased T-wave amplitude and area, caused ST depression, reduced heart rate (HR), and increased nonconducted P-wave arrhythmias. These changes were accompanied by increased pulmonary inflammation, lung resistance, and vagal tone, as indicated by changes in markers of HR variability (increased root of the mean of squared differences of adjacent RR intervals [RMSSD], low frequency [LF], high frequency [HF], and decreased LF/HF), and attenuated myocardial micro-RNA (RNA segments that suppress translation by targeting messenger RNA) expression. The low and intermediate concentrations of PM had less effect on the inflammatory, HR variability, and micro-RNA endpoints, but still caused significant reductions in HR. In addition, the intermediate concentration caused ST depression and increased QRS area, whereas the low concentration increased the T-wave parameters. Thus, PM-induced cardiac dysfunction is mediated by multiple mechanisms that may be dependent on PM concentration and myocardial vulnerability (this abstract does not reflect the policy of the United States Environmental Protection Agency).

Psychosocial modulators of angina response to myocardial ischemia

BACKGROUND

Although angina is often caused by atherosclerotic obstruction of the coronary arteries, patients with similar amounts of myocardial ischemia may vary widely in their symptoms. We sought to compare clinical and psychosocial characteristics associated with more frequent angina after adjusting for the amount of inducible ischemia.

METHODS AND RESULTS

From 2004 to 2006, 788 consecutive patients undergoing single-photon emission computed tomography stress perfusion imaging at 2 Seattle hospitals were assessed for their frequency of angina over the previous 4 weeks with the Seattle Angina Questionnaire and for a broad range of psychosocial characteristics. Among patients with demonstrable ischemia on single-photon emission computed tomography (summed difference score >or=2; n=191), angina frequency was categorized as none (Seattle Angina Questionnaire score=100; n=68), monthly (score=61 to 99; n=66), and weekly or daily (score=0 to 60; n=57). Using multivariable ordinal logistic regression, increasing angina was significantly associated with a history of coronary revascularization (odds ratio 2.24, 95% confidence interval 1.19 to 4.19), anxiety (odds ratio 4.72, 95% confidence interval 1.91 to 11.66), and depression (odds ratio 3.12, 95% confidence interval 1.45 to 6.69) after adjustment for the amount of inducible ischemia.

CONCLUSIONS

Among patients with a similar burden of inducible ischemia, a history of coronary revascularization and current anxiety and depressive symptoms were associated with more frequent angina. These results support the study of angina treatment strategies that aim to reduce psychosocial distress in conjunction with efforts to lessen myocardial ischemia.

Clinical aspects of silent myocardial ischaemia: with particular reference to diabetes mellitus

Silent ischaemia is a common, under-recognised condition that is associated with an adverse prognosis. It is a marker of significant underlying coronary artery disease and therefore of future cardiovascular events. It is more prevalent in the diabetic population and diagnosis is usually made by a positive exercise tolerance test, positive myocardial perfusion scan or stress echo. The basis of treatment, in diabetic and non-diabetic subjects, is risk factor modification and coronary revascularisation of prognostically important coronary disease. Diabetic patients should receive risk factor modification even in the absence of ischaemia. Detection of silent ischaemia allows patients with prognostically important disease to be offered further treatment. The difficulty lies in deciding who to investigate further for this surreptitious disorder. The following clinical markers are of predictive use in this regard: electrocardiographic changes; erectile dysfunction; peripheral vascular disease and cardiac autonomic neuropathy. Their presence should prompt further investigation for silent ischaemia. Conventional risk factors and breathlessness on exertion may also be helpful. We have proposed an algorithm for the detection, investigation and management of silent myocardial ischaemia in diabetic patients.

Increased non-conducted P-wave arrhythmias after a single oil fly ash inhalation exposure in hypertensive rats

BACKGROUND

Exposure to combustion-derived fine particulate matter (PM) is associated with increased cardiovascular morbidity and mortality especially in individuals with cardiovascular disease, including hypertension. PM inhalation causes several adverse changes in cardiac function that are reflected in the electrocardiogram (ECG), including altered cardiac rhythm, myocardial ischemia, and reduced heart rate variability (HRV). The sensitivity and reliability of ECG-derived parameters as indicators of the cardiovascular toxicity of PM in rats are unclear.

OBJECTIVE

We hypothesized that spontaneously hypertensive (SH) rats are more susceptible to the development of PM-induced arrhythmia, altered ECG morphology, and reduced HRV than are Wistar Kyoto (WKY) rats, a related strain with normal blood pressure.

METHODS

We exposed rats once by nose-only inhalation for 4 hr to residual oil fly ash (ROFA), an emission source particle rich in transition metals, or to air and then sacrificed them 1 or 48 hr later.

RESULTS

ROFA-exposed SH rats developed non-conducted P-wave arrhythmias but no changes in ECG morphology or HRV. We found no ECG effects in ROFA-exposed WKY rats. ROFA-exposed SH rats also had greater pulmonary injury, neutrophil infiltration, and serum C-reactive protein than did ROFA-exposed WKY rats.

CONCLUSIONS

These results suggest that cardiac arrhythmias may be an early sensitive indicator of the propensity for PM inhalation to modify cardiovascular function.

Silent myocardial ischemia

Although much progress has been made in reducing mortality from ischemic cardiovascular disease, this condition remains the leading cause of death throughout the world. This might in part be due to the fact that over half of patients have a catastrophic event (heart attack or sudden death) as their initial manifestation of coronary disease. Contributing to this statistic is the observation that the majority of myocardial ischemic episodes are silent, indicating an inability or failure to sense ischemic damage or stress on the heart. This review examines the clinical characteristics of silent myocardial ischemia, and explores mechanisms involved in the generation of angina pectoris. Possible mechanisms for the more common manifestation of injurious reductions in coronary flow; namely, silent ischemia, are also explored. A new theory for the mechanism of silent ischemia is proposed. Finally, the prognostic importance of silent ischemia and potential future directions for research are discussed.

ST segment depression in hypertensive patients: a comparison of exercise test versus Holter ECG

Introduction:

This study compared ST segment depression (ST depression) during cycle ergometry (ergometry) versus simultaneous 24-hour ambulatory blood pressure measurement and electrocardiogram recording (24-h ABPM/ECG) during everyday life.

Methods:

In a German multicenter study, ergometry and 24-h ABPM/ECG records of 239 hypertensive patients were retrospectively analyzed. ST depression was defined as an ST segment depression (1 mm limb or chest recordings V1 to V6) in an incremental cycle ergometry, or 1 mm in the 24-h ABPM/ECG recording under everyday conditions. Blood pressure parameters at the onset of ST depression in the context of the respective method were compared.

Results:

18 patients had ST depression only in ergometry (group B), 23 had ST depression only during 24-h ABPM/ECG monitoring (group C) and 28 patients had ST depression with both methods (group D). Group A had no ST depression with any method. In group D, at the onset of ST depression with 24-h ABPM/ECG investigation, all parameters except diastolic blood pressure were significantly lower compared with the corresponding parameters at the onset of ST depression with ergometry (systolic blood pressure: 148 ± 19 vers 188 ± 35 mmHg, p × 0.001; heart rate: 93 ± 12 vs 120 ± 21 beat/min, p < 0.0001; double product: 13,714 ± 2315 vs 22,992 ± 3,985 mmHg/min), p < 0.0001).

Conclusion:

ST depressions during everyday life detected by 24-h ABPM/ECG are characterized by a substantially lower triggering threshold for blood pressure level parameters compared with ergometry. The two methods detecting ischemia do not replace but complement each other.

Clinical and detailed angiographic findings in patients with ambulatory electrocardiographic ischemia without critical coronary narrowing: results from the Asymptomatic Cardiac Ischemia Pilot (ACIP) Study

BACKGROUND

Patients with ambulatory electrocardiographic (AECG) ST-segment depression and critical coronary narrowing are known to be at increased risk for adverse outcome, but little is known about patients with AECG ST-segment depression without critical coronary narrowing.

HYPOTHESIS

The objectives of this study were to characterize the coronary angiographic pathology in patients with AECG ST-segment depression but without critical (< 50% diameter stenosis) coronary narrowing and to compare demographic and clinical findings in these patients with those enrolled in the Asymptomatic Cardiac Ischemia Pilot Study with AECG ST-segment depression and critical (> or = 50% diameter stenosis) coronary narrowing.

METHODS

Coronary angiograms from patients with AECG ST-segment depression were reviewed in a central laboratory and quantitative measurement of percent stenosis was performed. Clinical and angiographic comparisons were made between patients with and without critical coronary narrowing.

RESULTS

Patients without critical coronary narrowing (n = 64) were younger (p = 0.02), less likely to be male (p < 0.001) or to have risk factors for coronary atherosclerosis or a history of myocardial infarction (p < 0.001), and had fewer ischemic episodes per 24 h on the screening AECG (p = 0.02) than patients with critical coronary narrowing (n = 441). Of patients without critical narrowing, one half had angiographic evidence for coronary artery disease (> or = 20% stenosis) and 60% had an ejection fraction > 70%.

CONCLUSIONS

Patients with AECG ST-segment depression without critical coronary narrowing are heterogeneous, with half having measurable coronary artery disease. Demographically and clinically, they appear to be different than patients with AECG ST-segment depression with critical coronary narrowing.

[Long term electrocardiography (Holter monitoring)]

During the past almost 50 years Holter monitoring has become an established non-invasive diagnostic tool in clinical electrophysiology. It allows ECG recording independent of stationary monitoring facilities during daily life and, therefore, contains much information. In the beginning the main interest was directed towards quantitative and qualitative assessment of arrhythmias, their circadian behaviour, and the circadian behaviour of the heart rate. With advances in technology the analysis spectrum of Holter monitoring expanded, and it was used also for detection of silent myocardial ischaemia. New digital recorders and computers with large capacities made it possible to measure every single heart beat very accurately, which was a prerequisite for heart rate variability and QT-interval analysis, which provided new knowledge about the autonomic modulation of the heart rate and the circadian dynamicity of the QT interval, respectively. Beyond arrhythmia analysis Holter monitoring was increasingly used to assess prognosis in different cardiac conditions. It can also be valuable in assessing transient symptoms possibly related to arrhythmias or device dysfunction, which will not necessarily be revealed by simple device control.

The electrocardiogram as a prognostic tool for predicting major cardiac events

Among patients with cardiac disease, the identification of those who are at low risk and those who are at high risk for major cardiac events is crucial for a rational clinical management of individual patients. A correct noninvasive risk stratification of cardiac patients, in particular, has relevant clinical implications because it would avoid unnecessary exposure to potentially risky invasive diagnostic or interventional procedures in low-risk patients, whereas it would allow an appropriate aggressive diagnostic and therapeutic approach in high-risk patients. Furthermore, the appropriate identification of low- and high-risk patients would also have social and economic implications by favoring optimization of resource distribution and costs. A large number of studies in previous decades provided evidence that several methods and variables derived from the analysis of the electrocardiogram (ECG) are powerful predictors of major cardiac events in several clinical conditions. Despite that, there has been limited attention about how several of these findings can be used in clinical practice. Furthermore, in recent years, most studies about risk stratification of cardiac patients have mainly been focused on the use of a number of serum/plasma biomarkers with reduced attention to ECG variables. Surprisingly, however, there have been few attempts to establish whether the various proposed risk markers add any significant information to that obtainable from ECG methods. In this article, the evidence for the prognostic value of variables derived from the assessment of the ECG signal by several methods and techniques will be briefly reviewed. Because of the largeness of the topic, this review will be necessarily incomplete. Because most of the clinical research in this field concerned risk stratification of patients with coronary artery disease, the article will be largely focused on this population of patients. The role of ECG methods in specific cardiac diseases and, in particular, in the general population of asymptomatic subjects will be briefly discussed when believed appropriate and helpful. Furthermore, only major clinical events (ie, cardiac death, arrhythmic events, acute myocardial infarction) will be taken into account as end points in this article. Minor clinical events (eg, coronary revascularization procedures, coronary artery restenosis, recurrences of symptoms) are indeed less robust as end points because they are widely biased by subjective judgments.

Prevalence and prognostic implications of ST-segment deviations from ambulatory Holter monitoring after ST-segment elevation myocardial infarction treated with either fibrinolysis or primary percutaneous coronary intervention (a Danish Trial in Acute Myocardial Infarction-2 Substudy)

Ambulatory Holter monitoring has been shown to be useful in stratifying cardiovascular risk after acute myocardial infarction. However, it remains unclear whether ST-segment deviations might predict clinical outcomes in a population treated with primary percutaneous coronary intervention (PCI) compared with thrombolysis. Holter monitoring was initiated at discharge from ST-segment elevation myocardial infarction in 958 patients followed for 2,773 patient-years, randomized to immediate revascularization with either fibrinolysis (n=474) or PCI (n=484). The primary end point was all-cause mortality, and the secondary end point was a composite of death, reinfarction, and disabling stroke. The prevalences of ST-segment depression (STd) and ST-segment elevation (STe) were similar in patients treated with fibrinolysis or PCI (both p=NS). During follow-up, 58 patients died (primary PCI vs fibrinolysis hazard ratio 0.74, p=0.25). The secondary end point was reached in 113 patients (primary PCI vs fibrinolysis hazard ratio 0.66, p=0.03). In fibrinolysis-treated patients, mortality and the secondary end point were significantly higher in patients with STe (both end points p<0.001), an association that remained statistically significant after adjustment for age, gender, anterior infarction, beta-blocker treatment, left ventricular systolic function, and STd (p=0.03 and p=0.005, respectively). Significant associations were not observed for STd. In PCI-treated patients, there was no association between either STe or STd and outcome. In conclusion, immediate revascularization with PCI during STe myocardial infarction does not affect the subsequent prevalence of ST-segment deviation compared with fibrinolysis. However, although STe is an independent predictor of mortality and nonfatal major cardiovascular events in patients treated with fibrinolysis, it does not predict outcome after PCI, perhaps because of more complete revascularization.

Value and limitations of ambulatory ECG monitoring for assessment of myocardial ischemia

Ambulatory ECG monitoring (AEM) is the only available method to assess the presence and severity of myocardial ischemia during daily life. Several investigators have shown that the recording systems currently used can detect ischemic changes with similar accuracy as treadmill exercise testing. Ischemic changes on AEM are, however, present in only 40%-60% of patients with coronary artery disease (CAD) and positive exercise tests. For this reason, and because of the high day-to-day variability in daily ischemic changes, AEM cannot be used as a screening tool for detecting CAD or for evaluating severity of ischemia in individual patients. In patients with proven CAD, ischemic changes on AEM are associated with an adverse outcome in patients with stable and unstable ischemic syndromes, and in postmyocardial infarction patients. Suppression of daily ischemia seems to be associated with improved outcome. The mechanism of daily ischemia is not identical to exercise-induced ischemia. In addition to increased demand, which is a major contributor to AEM detected-ischemia, increased coronary tone also seems to play a major role. AEM has been shown to be a useful and reliable tool to assess the efficacy of various antiischemic drugs.

Long-term continuous external electrocardiographic recording: a review

Ambulatory electrocardiographic (AECG) monitoring is an essential tool in the diagnostic evaluation of patients with cardiac arrhythmias. Recent advances in solid-state technology have improved the quality of the ECG signals and new dedicated algorithms have expanded the clinical application of software-based AECG analysis systems. These advances, in addition to the availability of inexpensive large storage capacities, and very long-term continuous high-quality AECG monitoring, have opened new potential uses for AECG. New digital recorders have the capability of multichannel simultaneous recordings (from 3 to 12 leads) and for telemetred signal transduction. These possibilities will expand the traditional uses of AECG for arrhythmia detection, as arrhythmia monitoring to assess drug and device efficacies has been further defined by new studies. The analysis of transient ST-segment deviation still remains controversial, but considerably more data are now available, especially about the prognostic value of detecting asymptomatic ischaemia. Heart rate variability analysis has shown promise for predicting mortality rates in cardiac patients at high risk. We review recent advances in this field of non-invasive cardiac testing.

Silent myocardial ischemia: Recent developments

Silent myocardial ischemia is now in its fourth decade of recognition as a clinical syndrome within the spectrum of coronary artery disease. Prior decades have seen important research into the pathophysiology, detection, prevalence, prognosis, and therapy of this syndrome. More recent developments have continued to add data to each of these areas, with particular emphasis on the comparative value of various diagnostic procedures and the effect of therapy on prognosis. While controversy still exists concerning proper screening guidelines for the asymptomatic population, there is a growing consensus that some form of stress testing in high-risk individuals (ie, those with multiple coronary risk factors) is appropriate.

Effect of aggressive versus moderate lipid-lowering therapy on myocardial ischemia: the rationale, design, and baseline characteristics of the Study Assessing Goals in the Elderly (SAGE)

BACKGROUND

Patients with stable CHD who experience episodes of ischemia during routine daily activities are at increased risk of coronary events. Older patients are at a particularly high risk. Few trials have specifically investigated the effects of lipid-lowering therapy with statins in older patients.

METHODS

The SAGE trial is a prospective, randomized, double-blind, parallel-arm study enrolling men and women with stable CHD at 192 centers worldwide. Qualifying participants (aged 65-85 years; low-density lipoprotein cholesterol 100-250 mg/dL) have had at least 1 episode of myocardial ischemia with total ischemia duration >or=3 minutes on 48-hour ambulatory electrocardiographic (AECG) monitoring performed during routine daily activities. Participants have been randomized to either atorvastatin 80 mg/day (aggressive lipid lowering) or pravastatin 40 mg/day (moderate lipid lowering). The primary efficacy measure is the absolute change in the total duration of myocardial ischemic events on 48-hour AECG monitoring from baseline to month 12.

RESULTS

SAGE is fully enrolled and 893 patients have been randomized. The majority of the study participants are white (97%) men (69%). The mean age of the participants is 72 years. Most participants (94%) have a history of angina. Other high-risk patient groups included in the study are patients with hypertension (65%), patients with diabetes (23%), and patients with peripheral vascular disease (12%).

CONCLUSIONS

SAGE will evaluate the effect of aggressive versus moderate lipid lowering on the total duration of myocardial ischemia in older ambulatory patients with CHD. It is likely to provide valuable data on the benefits of statins in this patient population.

Long-term outcome of patients with silent versus symptomatic ischemia six months after percutaneous coronary intervention and stenting

OBJECTIVES

We sought to evaluate the incidence of silent ischemia versus symptomatic ischemia six months after percutaneous coronary intervention (PCI) and its impact on prognosis and to test the utility of myocardial perfusion single-photon emission computed tomography (SPECT), or MPS, for risk stratification in these patients.

BACKGROUND

Silent ischemia is frequent after PCI. However, little is known about silent ischemia and long-term outcome after PCI and stenting.

METHODS

In 356 consecutive patients with successful PCI and stenting and follow-up MPS after six months, long-term follow-up (4.1 +/- 0.3 years) was performed. The MPS images were interpreted by defining summed stress, rest, and difference scores (summed difference score [SDS] = extent of ischemia) and related to symptoms and outcome. Critical events included cardiac death, myocardial infarction, and target vessel revascularization.

RESULTS

Eighty-one patients (23%) had evidence of target vessel ischemia, which was silent in 62%. The only independent predictor of silent ischemia was SDS (odds ratio 0.64, p = 0.001). During follow-up, 67 critical events occurred. For patients with an SDS of 0, 1-4, and >4, the critical event rates were 17%, 29%, and 69%, respectively. Similarly, patients without ischemia, silent ischemia, and symptomatic ischemia had 17%, 32%, and 52% of critical events, respectively. Diabetes (relative risk 1.98, p = 0.03) and SDS (relative risk 1.2, p < 0.001) were independent predictors of critical events. The MPS image added incremental information for the prediction of critical events.

CONCLUSIONS

Six months after PCI and stenting, 23% of patients had target vessel ischemia, which was silent in 62%. Silent ischemia predicted a worse outcome than did no ischemia and tended to have a better outcome than symptomatic ischemia. This was closely related to the extent of ischemia. The SDS added incremental value to pre-scan findings with respect to diagnosis and prognosis, indicating the utility of MPS for risk stratification after PCI and stenting.

ST segment depression criteria and the prevalence of silent cardiac ischemia in hypertensives

The reported prevalence of silent cardiac ischemia as assessed by ambulatory electrocardiographic recording varies widely. The influence of the stringency of the analysis criteria has never been reported. We performed 24-hour, 12-lead ambulatory electrocardiographic recording in patients with hypertension but without proven coronary artery disease. The recordings were analyzed according to strict ST segment depression criteria adapted from the American College of Cardiology/American Heart Association guidelines and according to basic ST segment depression criteria adapted from studies with only concise descriptions of ambulatory electrocardiographic recording analysis. Also, we performed 24-hour ambulatory blood pressure monitoring. More than 4400 hours of ambulatory electrocardiographic recording and ambulatory blood pressure monitoring in 194 patients with hypertension were analyzed. Medication was withdrawn in 45% of the patients. The average systolic blood pressure during the day was 152+/-13 (mean+/-SD); diastolic blood pressure was 94+/-17 mm Hg. According to the basic ST segment depression criteria, we found a prevalence of silent ischemia of 11.3%, and with the strict criteria the prevalence was 5.2%. The patients who were considered positive according to the basic criteria but not according to the strict criteria (false-positive) in the majority of cases (58%) had depression of an elevated baseline ST segment. We found a lower prevalence of silent cardiac ischemia as assessed by ambulatory electrocardiographic recording than generally reported. The stringency of applied analysis criteria appear to play an important role in this outcome.

Silent cardiac ischemia

Between the extremes of those who have no coronary disease and those limited by it are those with documented ischemia but no symptoms. Treating these patients in the "murky middle" generates some important questions. Should we treat patients with no symptoms solely on the basis of test abnormalities? Can we make the asymptomatic person better? What interventions would we use to treat such a disorder? How do we justify the risk, inconvenience, and cost of these interventions? How do we measure the efficacy of our intervention? Treating the asymptomatic person can only be justified if we prevent future events through our intervention. The management of silent ischemia can serve as a model for handling other preventative measures. The following article describes the issues around silent cardiac ischemia and some of the insights obtained in the Asymptomatic Cardiac Ischemia Pilot (ACIP) Study.

Relationship between vascular dysfunction in peripheral arteries and ischemic episodes during daily life in patients with ischemic heart disease and hypercholesterolemia

BACKGROUND

It is well established that endothelial dysfunction is present in patients with ischemic heart disease and hypercholesterolemia. Some of these patients will have signs of transient myocardial ischemia during Holter monitoring. We sought to describe the correlation between daily life ischemia and signs of endothelial dysfunction as assessed by means of brachial vasoreactivity.

METHODS

We included in the study 131 patients with documented ischemic heart disease and a serum cholesterol level of > or =5 mmol/L before the institution of lipid-lowering treatment and dietary intervention.

RESULTS

Satisfactory 48-hour Holter recordings and ultrasound scans of the brachial artery were obtained in 119 patients. During 5712 hours of ambulatory monitoring, 181 episodes of transient ST-segment depression with a mean duration of 52 +/- 66 minutes were recorded in 31 patients. The mean percentage dilatation of the brachial artery after occlusion was 4.38% +/- 5.66%; after nitroglycerin administration, it was 13.86% +/- 7.06%. By means of Spearman correlation analysis, the number of ischemic episodes and degree of flow-mediated vasodilatation and nitroglycerin-mediated vasodilatation were significantly negatively correlated (r = -0.249, P =.006 and r = -0.302, P =.02, respectively). In a linear regression model, the presence of ischemic episodes was a significant predictor of impaired flow-mediated vasodilatation (beta = -3.31, P <.01), even after the adjustment for vessel size and classic cardiovascular risk factors.

CONCLUSIONS

These results indicate a significant relationship between ischemic episodes and vascular dysfunction in patients with ischemic heart disease and hypercholesterolemia and may justify an aggressive preventive therapy targeted directly at the endothelium.

Diagnostic and prognostic value of Holter-detected ST-segment deviation in unselected patients with chest pain referred for coronary angiography: a long-term follow-up analysis

OBJECTIVE

To evaluate the diagnostic and prognostic significance of ST-segment deviation detected by ambulatory Holter monitoring in unselected chest pain patients referred for coronary angiography.

METHODS

Two hundred seventy-seven patients (71% were men) who underwent coronary angiography for evaluation of chest pain were studied with 24-h ambulatory Holter monitoring within 72 h of angiography. A lumen diameter reduction of > or = 50% was considered coronary artery disease. The ST-segment deviation was defined as > or = 1-mm deviation from the baseline lasting > or = 1 min separated by a minimum of 1 min. The patients were followed up for 65 +/- 21 months (mean +/- SD) for occurrences of death, myocardial infarction, hospitalization for unstable angina, and need for revascularization.

RESULTS

Of the 277 patients, 223 (80%) had coronary artery disease. The prevalence of coronary artery disease was not significantly different in patients with (43 of 48 patients; 90%) and without (180 of 229 patients; 79%) Holter-detected ST-segment deviation. The diagnostic accuracy of Holter-detected ST-segment deviation in predicting the presence of coronary artery disease was poor (33%), with a sensitivity of 19% and a specificity of 91%. The presence of Holter-detected ST-segment deviation was not predictive of future cardiac events or death.

CONCLUSION

The ST-segment changes detected on ambulatory Holter monitoring are of limited value in identifying coronary artery disease and predicting the future adverse cardiac events or death in unselected patients with chest pain.

Correlation of ST-segment depression during ambulatory electrocardiographic monitoring with myocardial perfusion and left ventricular function

To assess the relation between silent ischemia and objective markers of ischemia we compared ambulatory electrocardiographic (AECG) monitoring, exercise stress testing, and technetium-99m methoxyisobutyl isonitrile single-photon emission computed tomography (SPECT) in 68 patients with coronary artery disease. ST-segment depression at AECG monitoring occurred in 40%, exercise testing was positive in 88%, and SPECT was abnormal in 98% of patients. Patients with ST-segment depression had a higher incidence of 3-vessel disease (70% vs 45%, p = 0.04), shorter duration of exercise (267 +/- 109 vs 416 +/- 167 seconds, p < 0.01), lower workload achieved (5.1 +/- 1.9 vs 7.6 +/- 2.8 METs, p < 0.0002), and a greater extent of ischemia at scintigraphy (p = 0.01). Patients with a total ischemic time of >30 minutes in a 24-hour period had a lower ejection fraction (48 +/- 21% vs 70 +/- 9%, p = 0.001), a higher perfusion index at rest (2.4 +/- 0.6 vs 1.6 +/- 0.6, p = 0.001), and a greater number of segments with fixed perfusion defects (4.1 +/- 3.7 vs 1.3 +/- 1.8, p = 0.02) in comparison with those who had a shorter ischemic time. We conclude that AECG monitoring fails to identify a substantial proportion of patients with objective markers of ischemia; however, ST-segment depression reflects more significant disease. Longer total ischemic time correlates with the area of myocardial damage but not with other markers of ischemia.

Silent ischaemia and hypertension

For many years now, silent ischaemia has been recognized as a distinct clinical entity, and its relevance in different patient groups has been established. However, a number of basic questions have not been answered. In explaining the pathophysiology of silent ischaemia, factors affecting both the demand and the supply side are now being recognized. With the exception of certain well-defined groups, it is not clear why some patients are mostly symptomatic, while other patients are predominantly asymptomatic. There appear to be many factors influencing the ischaemic pain threshold. Studies investigating the prevalence of silent ischaemia show a remarkably high prevalence of silent ischaemia in different patient groups. Patients with hypertension but without coronary artery disease form a specific and vulnerable high-risk population that is particularly prone to silent ischaemia. Since changes at the macrovascular level are not responsible, various factors negatively influencing either cardiac supply or demand have been investigated. A reduced coronary reserve is central in explaining the increased prevalence of silent ischaemia in hypertensives. Left ventricular hypertrophy renders meaningful detection of ST segment changes difficult, but a possible solution dealing with this problem is offered by applying more stringent criteria in terms of minimal ST depression in the definition of ischaemia. The treatment of silent ischaemia is largely the same as for angina pectoris, but whether therapy should be directed at elimination of all ischaemic episodes or only of symptomatic episodes depends on further prospective work addressing this question.

Treating ambulatory ischemia in coronary disease by manipulating the cell biology of atherosclerosis

Obstructive coronary artery disease is the most common cause of morbidity and mortality in the developed world. Our understanding of the pathobiology of coronary atherosclerosis provides us with new opportunities to reduce myocardial ischemia by interventions that address these mechanisms directly. These interventions include lipid-lowering therapies that improve local coronary vasomotion, inflammation, and the procoagulant state. These interventions have also been shown to result in important reductions in clinical events, including angina pectoris, myocardial ischemia and infarction, and death. Ambulatory electrocardiography provides a versatile and quantifiable measure of regional myocardial ischemia. Reductions in ischemia, as quantified by this diagnostic modality, are associated with improved clinical outcomes that may reflect improvements in the cellular pathophysiology of coronary atherosclerosis. This review discusses new information regarding the interactions between low-density lipoprotein cholesterol, the cell biology of atherosclerosis, and the activity of ischemia in patients with coronary artery disease.

The brain-heart axis in the perception of cardiac pain: the elusive link between ischaemia and pain

Angina pectoris is a common symptom and one that can have profound implications for the patient. However, it correlates poorly with the extent of myocardial ischaemia and with prognosis. In order to understand more fully the heterogeneity of the experience of chest pain, we have adopted the technique of functional neuroimaging, where positron emission tomography is used to measure regional cerebral blood flow as an index of regional neuronal activation, during myocardial ischaemia in patients with coronary artery disease. We have been able to delineate those brain areas that are involved in the perception of angina: the hypothalamus, periaquaductal grey, thalami and bilaterally the prefrontal cortex and in the left the inferior anterocaudal cingulate cortex. By studying patients with silent myocardial ischaemia, we have established that the silence is not merely a matter of impaired afferent signalling resulting from autonomic neuropathy, but that it is associated with a failure of transmission of signals from the thalamus to the frontal cortex. At the other end of the spectrum, we have studied patients with syndrome X, a condition of chest pain with ischaemic-like stress electrocardiography (ECG) but entirely normal coronary angiogram; (on the basis of our own and other data we consider an ischaemic aetiology to be most unlikely in this condition). In syndrome X, distinct patterns of cerebral activation were found with characteristic activation of the right anterior insula at its junction with the frontal operculum. In conclusion, we present a unified view of the cerebral handling of afferent signals from the heart throughout this spectrum of experience of chest pain, a view that accounts for the clinical features of the patients studied.

Risk stratification after acute myocardial infarction in the reperfusion era

Historically, risk stratification for survivors of acute myocardial infarction (AMI) has centered on 3 principles: assessment of left ventricular function, detection of residual myocardial ischemia, and estimation of the risk for sudden cardiac death. Although these factors still have important prognostic implications for these patients, our ability to predict adverse cardiac events has significantly improved over the last several years. Recent studies have identified powerful predictors of adverse cardiac events available from the patient history, physical examination, initial electrocardiogram, and blood testing early in the evaluation of patients with AMI. Numerous studies performed in patients receiving early reperfusion therapy with either thrombolysis or primary angioplasty have emphasized the importance of a patent infarct related artery for long-term survival. The predictive value of a variety of noninvasive and invasive tests to predict myocardial electrical instability have been under active investigation in patients receiving early reperfusion therapy. The current understanding of the clinically important predictors of clinical outcomes in survivors of AMI is reviewed in this article.

Cost estimates for treatment of cardiac ischemia (from the Asymptomatic Cardiac Ischemia Pilot [ACIP] study)

Costs for management of myocardial ischemia are enormous, yet comparison cost and outcome data for various ischemia treatment strategies from randomized trials are lacking and will require cost and resource utilization data from a large prospective trial. The Asymptomatic Cardiac Ischemia Pilot provided feasibility data for planning such a trial and an opportunity to estimate the long-term costs of different treatment strategies. Economic implications for ischemia management were compared in 558 patients with stable coronary artery disease and myocardial ischemia during both stress testing and daily life. Participants were randomized to 3 different initial treatment strategies and followed for 2 years. Based on cost trends over follow-up, costs for subsequent care were estimated. As expected, due to initial procedural costs, at 3 months, estimated costs for revascularization were approximately 10 times greater than costs for a medical care strategy. Extrapolated costs for anticipated resource consumption for care beyond 2 years, however, were approximately 2 times greater for an initial medical care strategy than for initial revascularization. This was due to increased need for drugs and hospitalizations for both late revascularizations and other ischemia-related events. Estimated costs for anticipated care in the medical strategies reached the anticipated cost of the revascularization strategy within 10 years. Because this cost-equal time period is well within the median life expectancy for such a patient population, these findings could have important public health implications and require testing in a full-scale prognosis trial. We anticipate that over the patients' life expectancy, early revascularization is likely to become either cost-neutral or cost-effective.

[The clinical management guidelines of the Sociedad Española de Cardiología in acute myocardial infarct]

In the recent years, new possibilities have emerged in the diagnosis and management of acute myocardial infarction with ST segment elevation and its complications. Moreover, a deep transformation has taken place in the health care system organization, particularly in aspects related to care of patients presenting non-traumatic chest pain, both in pre-hospital and hospital areas. All these issues warrant a consensus document in Spain dealing with the role that these important changes should play in the whole management of myocardial infarction patients. This document revises and updates all the main clinical issues of acute myocardial infarction patients from the moment they contact with the health care system outside the hospital until they return home, after staying at the coronary care unit and the general hospitalization ward. All those aspects are considered not only in the uncomplicated myocardial infarction but also in the complicated one. This review also includes a set of recommendations on structural and organisational aspects, mainly referred to the prehospital and emergency levels.

Three-year follow-up of patients with silent ischemia in the subacute phase of myocardial infarction after thrombolysis and early coronary intervention

In order to assess the prognostic value of silent myocardial ischemia in acute myocardial infarction after thrombolysis and early coronary angiography (14-48 h after start of thrombolysis) including percutaneous transluminal coronary angioplasty, if indicated, 126 patients underwent 24 h-Holter-monitoring in the early postinfarction period. The 24 h-Holter-recording was initiated directly after early coronary intervention (40+/-11 h after onset of symptoms). Of the 126 patients initially eligible for the study 29 had to be excluded from further analysis for clinical or methodical reasons. Of the remaining 97 patients, 10 (10%) had silent ischemia (group A) and 87/97 (90%) patients showed no significant ST-segment alterations. Both groups did not significantly differ from each other with regard to baseline clinical characteristics, severity of coronary artery disease and frequency of successful percutaneous transluminal coronary angioplasty. The left ventricular ejection fraction showed a trend towards lower values in patients with than in those without silent ischemia (47+/-15% vs. 55+/-13%, p=0.07). When both silent ischemia and left ventricular ejection fraction <40% were present, a subset of patients at high risk for cardiac death could be identified (specificity: 98%, positive predictive accuracy: 75%). By Kaplan-Meier analysis, significantly more cardiac deaths occurred in group A than in group B (30% vs. 6%, p<0.01) during the three-year follow-up (950+/-392 days) after acute myocardial infarction. Regarding the cardiac events during long-term follow-up (emergency percutaneous transluminal coronary angioplasty, coronary artery bypass grafting, non-fatal reinfarction, and cardiac death) there was no significant difference between both groups (30% vs. 18%, NS). In conclusion, Holter monitor-detected silent ischemia in the subacute phase of myocardial infarction after thrombolysis followed by early delayed coronary intervention occurs in 10% of the patients indicating either a residual ischemia in the infarcted zone despite a combined reperfusion strategy or a remote ischemic potential in case of multivessel disease. In this small selected group of infarct patients too, silent ischemia is to be considered as an important non-invasive parameter to predict cardiac death during long-term follow-up and provides valuable complementary information to left ventricular dysfunction, a well established prognostic marker in the postinfarction period.

Visceral chest pain in unstable angina pectoris and effects of transcutaneous electrical nerve stimulation. (TENS). A review

A substantial proportion of patients with chest pain referred to hospital, show signs of coronary artery disease. Anginal pain could be conceptualized as a warning signal for coronary artery disease and impending death. But, for many reasons this theory is partly disputed. Firstly, not all ischemic episodes are accompanied by anginal pain (silent ischemia). Secondly, chest pain indistinguishable from true angina pectoris may be the result of other abnormalities of thoracic viscera. Nevertheless acute severe cardiac ischemia often gives rise to anginal chest pain. Unstable angina pectoris is carrying a higher risk for future events in spite of intensive medical treatment. A special problem are patients awaiting coronary intervention because of severe ischemia and maximum medical treatment, who experience ischemic pain. New treatment regimens are needed for these patients. This review discusses the symptom of visceral pain from the heart, angina pectoris, its relation to ischemia and unstable angina pectoris. It also addresses the role of afferent nerve stimulation (transcutaneous electrical nerve stimulation, TENS) in the treatment of severe angina pectoris as well as recent findings of TENS applicability in unstable angina.

Prevalence of episodes of ST-segment depression among mild-to-moderate hypertensive patients in northern Italy: the Cardioscreening Study

OBJECTIVES

To assess the prevalence of episodes of ST-segment depression in a population of consecutive patients with mild-to-moderate essential hypertension who are free of clinical signs of coronary artery disease.

METHODS

The study involved 28 Italian centers that enrolled 414 hypertensive patients (aged 50-70 years; diastolic blood pressure > or = 95-115 mmHg or systolic blood pressure > or = 150-220 mmHg, or both, 10 days after withdrawal of medications). Silent myocardial ischemia was assessed by means of exercise stress testing and 48 h Holter monitoring. An ischemic episode was defined as a horizontal or downward sloping ST-segment depression > or = 100 microV, occurring 80 ms after the J point, and lasting for at least 1 min.

RESULTS

Of the 414 patients enrolled, 411 completed the exercise stress test. During the test significant ST-segment depression occurred for 25 patients (6.1%) and all episodes but one were asymptomatic and not associated with arrhythmias. Of the 396 patients for whom we analyzed a 48 h Holter recording, 43 (10.9%) had at least one episode of ST-segment depression and seven of these had also had one during the exercise stress test The median number of episodes per patient was five (range 1-19), median duration was 9 min (range 1-20 min), and the mean amplitude of the ST-segment depression was 190 +/- 180 microV. None of these episodes was associated with symptoms and all of them occurred under resting condition. Patients with (n = 61) and without (n = 335) ST-segment depression during Holter monitoring or exercise stress testing had similar ages (59 +/- 6 versus 58 +/- 6 years) and did not differ for tobacco smoking, plasma lipid levels, blood pressure values and prevalence of echocardiographic left ventricular hypertrophy (57% of patients had left ventricular mass indexes > or = 134 g/m2 for men and > or = 110 g/m2 for women in both groups). Women had a higher prevalence of ST-segment depression than did men during Holter monitoring [32 of 183 (17.5%) versus 11 of 213 (5.2%)], whereas the prevalences of ischemia during the exercise stress test were similar. Female sex was the only significant factor associated with the occurrence of silent myocardial ischemia [odds ratio 2.56 (95% confidence interval 1.40-4.71)].

CONCLUSIONS

Our results show that 15% of patients with mild-to-moderate hypertension, who are free of clinical signs of coronary artery disease, experience episodes of ST-segment depression during Holter monitoring or exercise stress testing. Most of these episodes are asymptomatic and are not associated with the severity of hypertension, the presence of left ventricular hypertrophy, and other risk factors for coronary artery disease. Episodes of ST-segment depression are more common for women than they are for men, particularly during Holter monitoring. The early detection of silent myocardial ischemia by Holter monitoring or by the exercise stress test might be useful for the identification of hypertensive patients who should be investigated further and administered a more specific treatment.

Prognostic significance of ST segment shift early after resolution of ST elevation in patients with myocardial infarction treated with thrombolytic therapy: the GUSTO-I ST Segment Monitoring Substudy

OBJECTIVES

We sought to study the relation between recurrent ST segment shift within 6 to 24 h of initial resolution of ST elevation after thrombolytic therapy and 30-day and 1-year mortality.

BACKGROUND

Rapid and stable resolution of ST segment elevation in relation to thrombolytic therapy in patients with an acute myocardial infarction is an indicator of culprit artery patency. Whether recurrence of ST segment shift during continuous ST monitoring after initial resolution is related to poor prognosis has not been studied.

METHODS

ST segment monitoring was performed within 30 min after thrombolytic therapy for acute myocardial infarction. The predictive value of a new ST segment shift (assessed as > or = 0.1-mV deviation from the baseline) 6 to 24 h after thrombolytic therapy was studied with respect to 30-day and 1-year mortality.

RESULTS

Of 734 patients, 243 had a new ST segment shift (33%). The 30-day mortality rate in patients with an ST shift (7.8%) was significantly higher than that in patients without an ST shift (2.25%, p = 0.001), as was the 1-year mortality rate (10.3% vs. 5.7%, respectively, p = 0.025). Multivariable analysis revealed an independent predictive value of ST shift with respect to 30-day mortality (p = 0.008), even after consideration of multiple clinical risk factors in the overall Global Utilization of Streptokinase and TPA for Occluded Coronary Arteries (GUSTO)-I mortality model (p = 0.0001). Moreover, the duration of the ST shift bore a direct relation with 1-year mortality (p = 0.008).

CONCLUSIONS

Detection of ST segment shift early after thrombolytic therapy for acute myocardial infarction is a simple, noninvasive means of identifying patients at high risk and is superior to other commonly assessed clinical risk factors. Thus, patients with a new ST shift after the first 6 h, but within 24 h, represent a high risk group that may benefit from more aggressive intervention, whereas patients without evidence of an ST shift represent a low risk subgroup.

Prognostic significance of myocardial ischemia detected by ambulatory electrocardiography, exercise treadmill testing, and electrocardiogram at rest to predict cardiac events by one year (the Asymptomatic Cardiac Ischemia Pilot [ACIP] study)

Myocardial ischemia identified by ambulatory electrocardiography (AECG), exercising treadmill testing, (ETT), or 12-lead electrocardiogram at rest is associated with an adverse prognosis, but the effect of improving these ischemic manifestations by treatment on outcome is unknown. The Asymptomatic Cardiac Ischemia Pilot (ACIP) study was a National Heart, Lung, and Blood Institute funded study to determine the feasibility of conducting a large-scale prognosis study and to assess the effect of 3 treatment strategies (angina-guided strategy, AECG ischemia-guided strategy, and revascularization strategy) in reducing the manifestations of ischemia as indicated by AECG and ETT. The study cohort for this database study consisted of 496 randomized patients who performed the AECG, ETT, and 12-lead electrocardiogram at rest at both the qualifying and week 12 visits. The effect of modifying ischemia by treatment on the incidence of cardiac events (death, myocardial infarction, coronary revascularization procedure, or hospitalization for an ischemic event) at 1 year was examined. In the 2 medical treatment groups (n = 328) there was an association between the number of ambulatory electrocardiographic ischemic episodes at the qualifying visit and combined cardiac events at 1 year (p = 0.003). In the AECG ischemia-guided patients there was a trend associating greater reduction in the number of ambulatory electrocardiographic ischemia episodes with a reduced incidence of combined cardiac events (r = -0.15, p = 0.06). In the revascularization strategy patients this association was absent. In the medical treatment patients the exercise duration on the baseline ETT was inversely associated with an adverse prognosis (p = 0.02). The medical treatment strategies only slightly improved the exercise time and the exercise duration remained of prognostic significance. In the revascularization group strategy patients this association was absent. Thus, myocardial ischemia detected by AECG and an abnormal ETT are each independently associated with an adverse cardiac outcome in patients subsequently treated medically.

Role of beta blockade in the treatment of myocardial ischemia

A number of antianginal drugs and therapeutic strategies are now available for the treatment of patients with coronary artery disease (CAD) and myocardial ischemia. Of the available antianginal drugs, beta blockers appear to be most effective in suppressing myocardial ischemia. The superior anti-ischemic efficacy of beta blockers can be explained by their beneficial actions on hemodynamic parameters, vasomotion, and platelet function. Compared with other anti-ischemic drugs, beta blockers appear to be more efficacious in reducing the magnitude of myocardial ischemia during routine daily activities. In addition, the results of recent studies indicate that treatment with beta blockers not only suppresses myocardial ischemia, but also improves the clinical outcome in patients with CAD. These beneficial effects, along with the well-demonstrated cardioprotective effects of beta blockade in the postinfarction period, clearly suggest that this class of anti-ischemic drugs is an ideal therapeutic choice in most patients with CAD.

Efficacy of mibefradil compared with amlodipine in suppressing exercise-induced and daily silent ischemia: results of a multicenter, placebo-controlled trial

BACKGROUND

Mibefradil is a new benzimidazolyl-substituted tetraline-derivative calcium antagonist. Its vasodilatory activity combined with an ability to lower heart rate without negative inotropic effects as well as its long duration of action make it a promising anti-ischemic agent.

METHODS AND RESULTS

Three hundred nine patients with coronary artery disease, stable angina pectoris, and positive exercise tests were randomized to receive mibefradil (50, 100, or 150 mg), amlodipine (10 mg), or placebo. The anti-ischemic effects of mibefradil on exercise test and silent ischemia parameters were assessed. At doses of 100 and 150 mg, mibefradil increased exercise duration (by 55.5 and 51.0 seconds, respectively; P<.001 for both), increased time to onset of angina (by 98.3 and 82.7 seconds, respectively; P<.001), and increased time to 1-mm ST depression (by 81.7 and 94.3 seconds, respectively; P<.001). By comparison, a 10 mg/d dose of amlodipine significantly improved only time to onset of angina (treatment effect: 38.5 seconds, P=.036). Mibefradil 100 mg and 150 mg decreased the number of episodes of silent ischemia (treatment effects: -3.1 and -3.6, respectively; P<.001) and the duration of silent ischemia (treatment effects: -9.2 minutes, P=.048, and -14.6 minutes, P=.002, respectively). The decrease in the number of episodes of silent ischemia was also statistically significant in the group receiving 10 mg of amlodipine (-1.5; P=.036).

CONCLUSIONS

Once-daily doses of 100 and 150 mg mibefradil were effective in improving exercise tolerance and reducing ischemic episodes during ambulatory monitoring in patients with coronary artery disease.

A pilot study of continuous ambulatory electrocardiography in patients donating blood for autologous use in elective coronary artery bypass grafting

BACKGROUND

A pilot study was conducted to evaluate the impact of a single autologous blood donation on the presence or absence of myocardial ischemic episodes in patients with coronary artery disease.

STUDY DESIGN AND METHODS

Fifty patients scheduled for elective coronary artery bypass grafting underwent two 24-hour periods of ambulatory electrocardiogram monitoring, one before and one after their first autologous blood donation. The presence or absence and the number, duration, and integral area of episodes of ST segment depression for each 24-hour monitoring period were determined.

RESULTS

Forty-two patients had legible electrocardiogram recordings for both monitoring periods. Of these, 36 patients (86%) had at least one episode of ST segment depression during any monitoring period. The number of patients who had at least one episode of ST segment depression before donation was not significantly different from the number of those who had at least one episode after donation (31 and 33 patients, respectively; p = 0.73).

CONCLUSION

Donating a unit of blood had no demonstrable effect on the presence or absence of myocardial ischemic episodes in this sample of 42 autologous blood donors with coronary artery disease. The results of this study should be validated in further trials.

Attenuation of severity of myocardial ischemia during repeated daily ischemic episodes

OBJECTIVES

The purpose of this study was to assess whether the severity of myocardial ischemia would be attenuated by repeated daily ischemic episodes, recorded by ambulatory electrocardiographic monitoring (AEM).

BACKGROUND

Repetitive ischemic episodes induced by brief coronary occlusions in animal experiments and in humans during balloon coronary angioplasty produce preconditioning. We wanted to assess whether this phenomenon also exists during daily ischemic episodes.

METHODS

Twenty-one patients with known coronary artery disease and ischemia on exercise testing and AEM were requested to walk a distance known to have previously caused myocardial ischemia on three consecutive occasions. Walking time was approximately 15 min and was followed by 5 min of rest.

RESULTS

Mean maximal heart rate during the three walks was similar; however, the mean maximal ST segment depression decreased significantly from 2.21 mm during the first walk to 1.61 mm and 1.43 mm, respectively, on the second and third walks (p = 0.001). Ischemia duration was also significantly reduced on the second and third walks by 56% from 514 to 228 and 254 s, respectively (p = 0.012). The heart rate at onset of ischemia (ischemic threshold) increased from 99 beats/min on the first walk to 101 beats/min on the second walk and to 106 beats/min on the third walk (p = 0.058).

CONCLUSIONS

This study demonstrated attenuation of myocardial ischemia with an associated increase in ischemic threshold in patients with repeated and adjacent ischemic episodes. This form of myocardial protection is likely to be encountered in patients during ordinary activity and may represent the clinical counterpart of myocardial preconditioning.

Assessment of ischemic changes by ambulatory ECG-monitoring: comparison with 12-lead ECG during exercise testing

The accuracy of commercially available ambulatory electrocardiographic monitoring (AEM) systems for reproducing ischemic changes has been questioned. Since these systems are widely used for evaluation of ST-segment changes, both for prognostic purposes and for assessment of the efficacy of antiischemic drugs, such doubts must be clarified. For this purpose, we recorded electrocardiograms (ECGs) during exercise testing, using split leads, simultaneously with a 12-lead electrocardiograph and with the Marquette AEM recorder. We studied 29 patients with proven coronary artery disease and positive exercise tests and 19 individuals with low likelihood of coronary artery disease and negative stress tests. All 29 patients who had ST-segment depression during exercise as recorded on the 12-lead ECG had ST-segment depression in at least one of the three AEM leads (resembling the V5, V3, and aVF leads of the 12-lead system). The maximal degree of ST-segment depression with AEM was similar to 12-lead ECG (2.3 mm and 2.1 mm, respectively). The best lead for ischemia detection with AEM was the V5 type, which detected ischemic changes in 26 of the 29 patients, while the 12-lead V5 detected ischemia in 24 patients. The inferior AEM lead detected ischemia in only 4 patients, while the aVF lead of the 12-lead ECG detected ischemia in 23 patients. Of the 19 patients with negative exercise tests only 1 patient had a 1-mm ST-segment depression on AEM. Thus, of the 48 patients studied, similar responses were observed in 47. The results of indicate that the Marquette AEM system is as accurate as the 12-lead ECG in detecting ischemic changes and in assessing their severity.

Relation between clinical, angiographic and ischemic findings at baseline and ischemia-related adverse outcomes at 1 year in the Asymptomatic Cardiac Ischemia Pilot study. ACIP Study Group

OBJECTIVES

We attempted to investigate the relation between patient characteristics and adverse outcome in patients with ischemia and clinically stable coronary artery disease (CAD).

BACKGROUND

Evidence suggests that cardiac ischemia, detected by exercise stress testing (ETT) and ambulatory electrocardiographic (AECG) monitoring during daily living, identifies a subgroup of patients at increased risk for adverse outcome, but the relation between these ischemia findings and clinical and angiographic characteristics is largely unknown.

METHODS

We examined the relation between clinical, angiographic and ischemia characteristics at entry with adverse outcome observed at 1 year in the 558 patients enrolled in the Asymptomatic Cardiac Ischemia Pilot (ACIP) study.

RESULTS

By the 12-month visit 13.1% of patients had an ischemia-related adverse clinical outcome that included death, nonfatal myocardial infarction or an ischemia-related hospital admission. Multivariate analysis identified only the number of AECG ischemic episodes at entry (odds ratio [OR] 1.06, 99% confidence interval [CI] 1.01 to 1.12, p = 0.002) as an independent predictor of outcome. Assignment to revascularization (as opposed to an initial medical treatment strategy) showed a trend (OR 0.56, 99% CI 0.26 to 1.2, p = 0.05). None of the other baseline clinical, exercise or angiographic variables examined provided additional information relative to adverse outcome.

CONCLUSIONS

Determinants of adverse outcome, among clinically stable patients with CAD and ischemia induced by stress and daily life were magnitude of AECG ischemia before treatment and, possibly, initial treatment assignment. Among the many other characteristics examined, including age, symptom status and angiographic and exercise variables, none contributed additional independent prognostic information. These two simple variables, which may be modifiable, need further study in a larger trial.